engleski

2D GISAXS Analysis of Morphology in Nanostructured Cerium/Vanadium Oxide Thin Films

Thin films of mixed cerium and vanadium oxides were prepared by sol-gel process and dip-coating on glass substrates. The applications of these films as electrodes in electrochromic devices make specific demands upon their morphology and structural properties. The information about the film performance quality was obtained by electrochemical measurements performed under lithium intercalation. The aim of this work was to investigate which particular properties of structure and film morphology are characteristic for the films with best electrochemical measurement results and how the processing of the film material, as well as the intercalation of small ions, affects its properties. As the films were deposited on glass substrates, a non-destructive technique for examination was required. One of such techniques is the grazing-incidence small-angle X-ray scattering (GISAXS). It is particularly suitable for porous nanostructured films as ours. The GISAXS measurements were performed at the synchrotron ELETTRA in Trieste, Italy. Two-dimensional GISAXS spectra for each film were measured at different grazing angles. By varying the grazing-incidence angle, different regions of the film can be probed. The surface and bulk contributions to scattering, as different functions of sample to scattering angle orientation, can be clearly distinguished. Scattering measurements with two-dimensional detectors also allow a specific film depth-structural profiling. Besides the estimation of the primary morphological characteristics - the average nano-size of the scatterers and the properties of the inner scatterer/pore surface, such measurements can give information about the orientation of the scatterers, which depends on their position in film. The results of the described scattering measurements for thermally processed films of mixed cerium and vanadium oxides with different morphologies, before and after intercalation of lithium ions, are presented.

GISAXS; nanostructured thin films; V/Ce oxides

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